US20120199161A1 - Apparatus and a method for cleaning of a nuclear fuel element - Google Patents
Apparatus and a method for cleaning of a nuclear fuel element Download PDFInfo
- Publication number
- US20120199161A1 US20120199161A1 US13/499,093 US201013499093A US2012199161A1 US 20120199161 A1 US20120199161 A1 US 20120199161A1 US 201013499093 A US201013499093 A US 201013499093A US 2012199161 A1 US2012199161 A1 US 2012199161A1
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- Prior art keywords
- fuel element
- flow
- inner space
- fuel
- opening
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
- G21C19/20—Arrangements for introducing objects into the pressure vessel; Arrangements for handling objects within the pressure vessel; Arrangements for removing objects from the pressure vessel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/06—Devices or arrangements for monitoring or testing fuel or fuel elements outside the reactor core, e.g. for burn-up, for contamination
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
- G21C19/02—Details of handling arrangements
- G21C19/04—Means for controlling flow of coolant over objects being handled; Means for controlling flow of coolant through channel being serviced, e.g. for preventing "blow-out"
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Definitions
- the present invention relates to an apparatus and a method for cleaning of a nuclear fuel element in a liquid filled space, wherein the fuel element comprises an internal space with an opening, and wherein the apparatus comprises a connecting element, which is adapted to be connected to a portion of the fuel element, which comprises the opening and flow means that is adapted to create, at least during a part of a cleaning process of the fuel element, a liquid flow through the inner space of the fuel element via said opening.
- Nuclear fuel elements for a BWR have a tubular shape and have an inner space that comprises spacers, fuel rods, etc.
- BWR Biting Water Reactor
- metal particles, flakes, fibers, etc. may be formed, which during subsequent operation can be transported by the reactor water to the reactor tank.
- particles may fall down into the reactor tank.
- filters are generally positioned at appropriate places where the reactor water passes. Small particles however, can become trapped inside the fuel elements and cause abrasion damage to sensitive parts such as the fuel rods. Particles that fasten to the insides of the fuel elements do not circulate with the reactor water and, therefore, they can not be captured by conventional filters.
- the reactor water contains impurities derived mainly from corroded materials.
- impurities in the reactor water form deposits on the outer surfaces of the fuel rods. The deposits result in the reactor water experiencing an increased pressure drop in the fuel elements and a reduced heat exchange with the fuel rods.
- an apparatus that allows cleaning of a nuclear fuel element in a liquid filled space in a simple and effective way is provided.
- Such cleaning is achieved with the apparatus initially defined as comprising a flow channel.
- the flow channel has an opening in connection with a connecting element.
- a flow means is adapted to create, at least during a part of a cleaning process of the fuel element, a liquid flow from the inner space of the fuel element to the flow channel of the apparatus.
- a filter element is positioned in the flow channel, the filter element being adapted to capture particles and deposits that are transported with the liquid flow from the inner space of the fuel element. Spacers, fuel rods and other components in the fuel element form relatively narrow passages for the circulating reactor water. In order to detach particles that fasten inside the fuel element, the apparatus is thus connected to the fuel elements. When the liquid means of the apparatus is activated a liquid flow is created through the fuel element.
- the flow is alternating so that the particles that have fastened inside the fuel element are wrenched loose.
- particles and other deposits on particularly the fuel rods inside the fuel element can be detached and transported by the liquid flow out of the fuel element.
- the apparatus comprises the flow channel, which has an opening in connection to the connecting element and in which the flow means is adapted to create, at least during a part of a cleaning process of the fuel element, a liquid flow from the inner space of the fuel element to the flow channel of the apparatus. Thereby, the liquid from the inner space of the fuel element can be sucked into the apparatus.
- the apparatus further comprises a filter element in the flow channel, which is adapted to capture particles and deposits that are transported by the liquid flow from the inner space of the fuel element. By arranging a fine mesh filter element in the flow passage, the filter element can also capture relatively small particles that are detached from the inner space of the fuel element.
- the filter element is advantageously removably mounted in the apparatus so that it is replaceable. Thereby, it can be removed and emptied of particles or replaced with a new one after use.
- the flow means is adapted to create a liquid flow through the inner space of the fuel element, which varies according to a predetermined program during a cleaning process of the fuel element. In order to detach particles and deposits in an effective manner, the flow through the fuel element is varied. This can be done by a preliminary pre-determined program. Special programs can be used for cleaning fuel elements of different kinds.
- the flow means is advantageously adapted to create an intermittent liquid flow through the inner space during a cleaning process of the fuel element. By periodically interrupting the flow through the fuel element during a cleaning process, an intermittent liquid flow through the fuel element is created, which detaches particles and deposits from the inner space of the fuel element.
- the flow means includes a pump, which is arranged in the flow channel.
- One such suitable pump can suck a liquid flow through the fuel element.
- a flow valve may be arranged in the flow channel in a position upstream of the pump with respect to an intended flow direction in the flow channel, the flow valve being adjustable to a first position in which the flow valve prevents the pump from sucking liquid from the inner space of the fuel element and to a second position in which the flow valve allows the pump to suck liquid from the inner space of the fuel element.
- the flow valve has a construction so that in a first position, the pump is connected with an opening to the surrounding liquid.
- the flow valve thus supplies the pump with an alternative source from which the pump can suck liquid when the connection with the fuel element is interrupted. Therefore, the pump does not need to be turned off when the flow valve is set in the first position.
- the flow valve has a construction so that it in the first position connects the inner space of the fuel element with an opening to the surrounding liquid.
- the flow valve interrupts the connection of the pump with the fuel element, there is a liquid flow in the fuel element.
- the flow valve creates in this case an alternative route for this liquid flow.
- the liquid flow in the fuel element is therein not slowed abruptly when the flow valve is converted to the first position.
- the apparatus comprises a force element that is adapted to set the flow valve in the first position and in the second position.
- this force element comprises a first component, which operates with continuous power to set the flow valve in the first position and a second component, which in an activated state operates in an opposite direction with more power than the first component in order to set the flow valve in the second position.
- the first component can be a spring element and the second component can be a pneumatic cylinder.
- the present invention is not so limited, as other types of components can be used to set the flow valve between the first position and the second position.
- the apparatus comprises a joining portion that allows for a removable connection of the connecting elements with different shapes.
- a tight connection is established between the connecting element and the fuel element.
- the apparatus can be provided with different types of connecting elements that have a shape adapted to a specific type of fuel elements.
- the connecting element can comprise a cup-shaped portion that is adapted to be set on or slipped over an end portion of the fuel element. Such a cup-shaped portion enables establishing a tight connection between the apparatus and the fuel element.
- the apparatus can comprise a gripping portion that is adapted to be gripped by a hoisting device in order to lift the apparatus to a connecting position on a fuel element and in order to lift the apparatus from the connecting position on the fuel element after a cleaning process.
- An existing charging machine in a reactor facility can be used in order to apply and move the apparatus between cleaning processes of individual fuel elements in a reactor tank.
- Another aspect of the present invention resides in a method for cleaning a nuclear fuel element in a liquid filled space, wherein the fuel element comprises an inner space with an opening.
- the method comprises the steps of connecting an apparatus to a portion of the fuel element, which comprises an opening, and creating, at least during a part of a cleaning process of the fuel element, a liquid flow through an inner space with help of the apparatus, to create, at least during a part of a cleaning process of the fuel element, a liquid flow from the inner space of the fuel element to a flow channel of the apparatus, which has an opening in connection with the connecting element.
- the method further comprises the step of capturing particles and deposits transported by the liquid flow from the inner space of the fuel element into a filter element in the flow channel of the apparatus. With such a liquid flow, particles and deposits can be detached from the inner space of the fuel element and be captured in the filter element.
- an intermittent liquid flow through the inner space of the fuel element is created with the help of the attached apparatus.
- a cleaning process of the inner space of the fuel element is provided.
- the method can also comprise the step of connecting the apparatus to a fuel element, which is arranged in a reactor tank.
- the fuel elements do not need to be lifted out of the reactor tank when they are to be cleaned.
- FIG. 1 is a cutaway view of an apparatus according to the present invention in a reactor tank
- FIG. 2 is a side view of the apparatus in a position when the apparatus is connected to a fuel element
- FIG. 3 is a cross-sectional view through a filter element and a flow valve of the apparatus when the apparatus is in a first position
- FIG. 4 is a cross-sectional view through the apparatus when the flow valve has shifted to a second position.
- FIG. 1 shows a reactor tank 1 for a boiling water reactor BWR.
- the reactor tank 1 is shown in an open position and is arranged at a bottom surface of a reactor pool 2 .
- the reactor tank 1 and the reactor pool 2 are filled with water.
- a service bridge 3 spans over the reactor pool 2 .
- the service bridge 3 is provided with a movable charging machine 4 having a telescopic boom 5 with which it is possible to lift components up and down in the reactor tank 1 .
- the reactor tank 1 has been partially emptied of internal components.
- the internal components, which are lifted out of the reactor tank 1 can be placed in different positions in the reactor pool 2 .
- the fuel core which is arranged in a moderator tank 6 , is in this case left in the reactor tank 1 .
- a frame 7 forms a grid at an upper portion of the moderator tank 6 that defines the positions of a large number of fuel elements 8 .
- FIG. 1 further shows an apparatus 9 , which is adapted to clean internal particles and deposits from the fuel elements 8 .
- the apparatus 9 is applied with help of the charging machine 4 at an upper end portion of the fuel elements 8 in the reactor tank 1 .
- the fuel elements 8 are in this case left in the reactor tank 1 . It is possible, however, to lift up the fuel elements 8 and apply the apparatus 9 at the fuel elements 8 in an arbitrary position in the reactor pool 2 or in a connecting fuel pool.
- FIG. 2 shows the apparatus 9 and the top portion of a fuel element 8 in more detail.
- the fuel elements 8 comprise elongated tubular elements with an inner space 8 a , which contain fuel rods 8 c and spacers to keep the fuel rods in a desired mutual position in the inner space 8 a .
- a top plate 8 d holds a top end of the fuel rods 8 c in a desired position.
- the hot fuel rods 8 c heat up the reactor water that circulates through the inner space 8 a .
- the resulting steam and the heated water rise up in the inner space 8 a and out through an outlet opening 8 b at an upper end of the fuel elements 8 .
- New reactor water is fed into the inner space 8 a via an inlet opening, which is situated at a lower end of the fuel elements 8 .
- the apparatus 9 has a relatively elongated construction and comprises at a first end a gripping portion 10 that is adapted to be gripped by the charging machine 4 when the apparatus 9 is applied to the fuel element 8 .
- the apparatus 9 comprises at a second opposite end, a connecting element in the form of an intake cover 11 .
- the intake cover 11 has a cup-shaped portion with an internal shape and size that corresponds substantially to the outer shape and size of the upper end portion of the fuel element 8 .
- the intake cover 11 can thereby (with help of the charging machine 4 ) be lowered down and placed on or otherwise be affixed to the top end portion of the fuel element 8 .
- the intake cover 11 can be provided with suitable shaped control surfaces to facilitate positioning of the intake cover 11 on the fuel element 8 .
- the apparatus 9 comprises an elongated flow channel 12 , which extends from an inlet opening 13 in the intake cover 11 to an outlet opening 14 in an outlet portion 15 .
- the gripping portion 10 is in this case attached to the outlet portion 15 .
- the outlet portion 15 has a curved shape so that the outlet opening 14 is located alongside the gripping portion 10 .
- the device comprises a schematically shown pump 16 , which is adapted to transport the reactor water in the flow channel 12 . Between the pump 16 and the intake cover 11 , the apparatus 9 comprises a tubular portion 17 that encloses a filter and a tubular portion 18 that encloses a flow valve. The flow valve is controlled by a force element 19 .
- FIGS. 3 and 4 show cross-sectional views of the above mentioned tubular portions 17 , 18 of the apparatus 9 .
- the tubular portion 17 comprises one internal wall element 20 forming a space for receiving a filter element 21 , which may include a filter basket.
- the tubular portion 17 is attached by means of removable attachment elements, such as screws 22 .
- the tubular portion 17 can be removed from the apparatus when the filter element 21 needs to be cleaned or replaced.
- the tubular portion 18 comprises a flow valve in the form of a shiftably arranged valve body 23 .
- the valve body 23 comprises a cylindrical formed wall element and an internal wall portion 24 that divides an internal space of the valve body 23 into a first chamber 25 and a second chamber 26 .
- the first chamber 25 is provided with a peripheral opening 25 a .
- the second chamber 26 is provided with a first peripheral opening 26 a and several other smaller peripheral openings 26 b arranged at a different level than the first peripheral opening 26 a .
- a radially protruding control element 27 is firmly attached to the valve body 23 .
- the force elements 19 constitute a pneumatic cylinder 19 a and a spring element 19 b .
- the pneumatic cylinder 19 a is firmly attached to the apparatus 9 by means of a mounting element 28 and has a movable portion that is attached to the control element 27 .
- the spring element 19 b is, at one end, firmly attached to the apparatus 9 by means of a mounting element 29 and connected to the control element 27 at an opposite end.
- the spring element 19 b operates to shift the control element 27 and the valve body 23 downward to a first position as is shown in FIG. 3 .
- the pneumatic cylinder 19 When the pneumatic cylinder 19 is activated the control element 27 shifts upwards against the effect of the spring element 19 b , to a second position as is shown in FIG. 4 .
- the tubular portion 18 which encloses the valve body 23 has a first opening 30 , a second opening 31 and a third opening 32 .
- a flow element 33 is arranged around the tubular portion 18 at the height of the first opening 30 and the third opening 32 .
- the tubular portion 18 comprises at a lower end a joining portion 34 for application of an intake cover 11 .
- the joining portion 34 can comprise threads 35 or other mounting elements that allow a removable application of an intake cover 11 . Thereby, different intake covers 11 with suitable shapes can be attached to the apparatus 9 when the apparatus is to be connected to different types of fuel elements 8 .
- the apparatus 9 When the fuel elements 8 in a reactor tank 1 are to be cleaned, the apparatus 9 is attached with help of the grip handle 10 of a gripper of the charging machines telescopic boom 5 .
- the charging machine 4 moves the apparatus 9 to a position substantially vertically above the fuel elements 8 to be cleaned with help of coordinate information or with information from cameras or similar detection elements, which are arranged at appropriate positions on the apparatus 9 .
- the apparatus 9 is then immersed into the fuel element 8 so that the intake cover 11 encloses the upper end portion of the fuel element 8 and an opening 8 b for the inner space of the fuel element 8 a .
- the pump 16 When the apparatus 9 is connected in a desired way to the fuel element 8 , the pump 16 is activated. This can be done by an operator by means of a suitable control device.
- the operator can stand on the maneuver bridge 3 or in position at the side of the reactor pool 2 .
- the control device can be equipped with cables that transmit control signals and power to the pump 16 .
- the valve body 23 When the pump 16 is activated, the valve body 23 is preferably in the first position as is shown in FIG. 3 . In this position, the opening of the valve body 25 a to the first chamber 25 is located in a corresponding position as the first opening of the tubular portion 30 . Thereby, the pump 16 sucks in, in this case, the surrounding reactor water via the openings 30 , 25 a to the first chamber 25 . From the first chamber 25 , the reactor water is sucked further into the flow channel of the apparatus 12 up to the tubular portion 17 and down into the compartment with the filter element 21 . The reactor water is then sucked through the filter element 21 and further upwards in the flow channel 12 in the direction of the pump 16 according to the arrows in FIG. 3 .
- the reactor water is pressed upwards in the flow channel 12 and out through the outlet opening 14 in the outlet portion 15 .
- the second chamber of the valve body 26 is in constant contact with the intake cover 11 and the inner space of the fuel element 8 a .
- the fuel rods can have a residual elevated temperature, which creates an upward flow of the reactor water through inner space of the fuel element 8 a .
- Such a liquid flow is routed from the inner space of the fuel element 8 a to the second chamber of the valve body 26 .
- the other smaller openings of the second chamber 26 b of the valve body 26 are arranged in a position that corresponds to the position of the third opening of the tubular portion 32 .
- the pneumatic cylinder 19 a is activated.
- the pneumatic cylinder 19 a provides a force on the control element 27 so that the valve body 23 is set to the second position as is shown in FIG. 4 .
- the second chamber of the valve body 26 connects, via opening 26 a , to the second opening of the tubular portion 31 .
- the second opening of the tubular portion 31 is connected to a channel portion 36 , which is connected to the pump 16 .
- the connection between the second chamber 26 and the surrounding reactor water is interrupted because the opening of the second chamber 26 b is shifted from the third opening of the tubular portion 32 .
- the connection between the first chamber 25 with the surrounding water reactor is interrupted because the first opening of the chamber 25 a is shifted from the first opening of the tubular portion 30 . Accordingly, the pump 16 can no longer suck in the reactor water through the first opening of the tubular portion 30 .
- the pump 16 sucks in the reactor water from the inner space of the fuel element 8 a .
- the reactor water is sucked into the apparatus 9 with help of the intake cover 11 , which is connected to the upper end portion of the fuel elements 8 .
- the reactor water is routed from the intake cover 11 into the flow channel of the apparatus 12 via inlet opening 13 . Thereafter, the reactor water reaches the second chamber 26 .
- the reactor water is sucked into the channel portion 36 from the tubular portions 18 and from the second chamber 26 .
- the reactor water enters the second chamber 26 through the openings 26 a , 31 . Thereafter, the reactor water is sucked up to the filter element 21 . Any particles or deposits from the fuel element 8 are trapped in the filter element 21 .
- the reactor water is pumped further up and out through outlet opening 14 in the outlet portion 15 .
- the pneumatic cylinders 19 a are de-activated, and the valve body 23 is shifted back to the first position by the spring element 19 b .
- the valve body 23 is shifted a predetermined number of times, which may be within the range of 5-15 times, between the first position and the second position.
- a cleaning process of a fuel element of the present apparatus 9 comprises thus sucking the reactor water through the inner space of the fuel element 8 a with a pump 16 . Thereby, a liquid flow through the fuel element 8 is created that can detach any particles fastened inside the fuel element and deposits formed on the fuel rod surfaces. To further enhance this effect, the valve body 23 of the apparatus 9 is shifted several times between the above mentioned positions. Thereby, an intermittent flow through the inner space of the fuel element 8 a is provided. The intermittent flow of the reactor water through the inner space of the fuel element 8 a enhances the apparatus's ability to detach particles fastened inside the fuel element 8 and to detach deposits from the fuel rods surfaces 8 c .
- Such detached particles and deposits are transported by the reactor water into the apparatus 9 , where they are captured in the filter element 21 .
- the charging machine 4 is activated, which moves the apparatus 9 to a not yet cleaned fuel element 8 of the reactor core.
Abstract
Description
- The present invention relates to an apparatus and a method for cleaning of a nuclear fuel element in a liquid filled space, wherein the fuel element comprises an internal space with an opening, and wherein the apparatus comprises a connecting element, which is adapted to be connected to a portion of the fuel element, which comprises the opening and flow means that is adapted to create, at least during a part of a cleaning process of the fuel element, a liquid flow through the inner space of the fuel element via said opening.
- Nuclear fuel elements for a BWR (Boiling Water Reactor) have a tubular shape and have an inner space that comprises spacers, fuel rods, etc. In connection with maintenance and repair work in systems that are connected to the reactor tank, there is a risk that metal particles, flakes, fibers, etc. may be formed, which during subsequent operation can be transported by the reactor water to the reactor tank. Also during times when the reactor tank is opened, there is a risk that particles may fall down into the reactor tank. During a subsequent operation, such particles could then be circulated in the reactor tank with the reactor water. In order to capture such particles, filters are generally positioned at appropriate places where the reactor water passes. Small particles however, can become trapped inside the fuel elements and cause abrasion damage to sensitive parts such as the fuel rods. Particles that fasten to the insides of the fuel elements do not circulate with the reactor water and, therefore, they can not be captured by conventional filters.
- The reactor water contains impurities derived mainly from corroded materials. When the reactor water during operation comes in contact with and is heated by the fuel rods, such impurities in the reactor water form deposits on the outer surfaces of the fuel rods. The deposits result in the reactor water experiencing an increased pressure drop in the fuel elements and a reduced heat exchange with the fuel rods.
- In one aspect of the present invention, an apparatus that allows cleaning of a nuclear fuel element in a liquid filled space in a simple and effective way is provided.
- Such cleaning is achieved with the apparatus initially defined as comprising a flow channel. The flow channel has an opening in connection with a connecting element. A flow means is adapted to create, at least during a part of a cleaning process of the fuel element, a liquid flow from the inner space of the fuel element to the flow channel of the apparatus. A filter element is positioned in the flow channel, the filter element being adapted to capture particles and deposits that are transported with the liquid flow from the inner space of the fuel element. Spacers, fuel rods and other components in the fuel element form relatively narrow passages for the circulating reactor water. In order to detach particles that fasten inside the fuel element, the apparatus is thus connected to the fuel elements. When the liquid means of the apparatus is activated a liquid flow is created through the fuel element. By creating a liquid flow that may be greater or less than the liquid flow through the fuel element during operation, such particles can be detached and transported with the liquid flow out of the fuel element via the opening. Advantageously, the flow is alternating so that the particles that have fastened inside the fuel element are wrenched loose. With such a liquid flow, particles and other deposits on particularly the fuel rods inside the fuel element can be detached and transported by the liquid flow out of the fuel element.
- According to one aspect illustrated herein the apparatus comprises the flow channel, which has an opening in connection to the connecting element and in which the flow means is adapted to create, at least during a part of a cleaning process of the fuel element, a liquid flow from the inner space of the fuel element to the flow channel of the apparatus. Thereby, the liquid from the inner space of the fuel element can be sucked into the apparatus. The apparatus further comprises a filter element in the flow channel, which is adapted to capture particles and deposits that are transported by the liquid flow from the inner space of the fuel element. By arranging a fine mesh filter element in the flow passage, the filter element can also capture relatively small particles that are detached from the inner space of the fuel element. The filter element is advantageously removably mounted in the apparatus so that it is replaceable. Thereby, it can be removed and emptied of particles or replaced with a new one after use.
- According to another aspect illustrated herein, the flow means is adapted to create a liquid flow through the inner space of the fuel element, which varies according to a predetermined program during a cleaning process of the fuel element. In order to detach particles and deposits in an effective manner, the flow through the fuel element is varied. This can be done by a preliminary pre-determined program. Special programs can be used for cleaning fuel elements of different kinds. The flow means is advantageously adapted to create an intermittent liquid flow through the inner space during a cleaning process of the fuel element. By periodically interrupting the flow through the fuel element during a cleaning process, an intermittent liquid flow through the fuel element is created, which detaches particles and deposits from the inner space of the fuel element.
- According to another aspect illustrated herein, the flow means includes a pump, which is arranged in the flow channel. One such suitable pump can suck a liquid flow through the fuel element. A flow valve may be arranged in the flow channel in a position upstream of the pump with respect to an intended flow direction in the flow channel, the flow valve being adjustable to a first position in which the flow valve prevents the pump from sucking liquid from the inner space of the fuel element and to a second position in which the flow valve allows the pump to suck liquid from the inner space of the fuel element. With such a flow valve, an intermittent liquid flow through the fuel element can be created in a simple manner and without the pump being turned off and turned on.
- According to another aspect illustrated herein, the flow valve has a construction so that in a first position, the pump is connected with an opening to the surrounding liquid. The flow valve thus supplies the pump with an alternative source from which the pump can suck liquid when the connection with the fuel element is interrupted. Therefore, the pump does not need to be turned off when the flow valve is set in the first position. Advantageously, the flow valve has a construction so that it in the first position connects the inner space of the fuel element with an opening to the surrounding liquid. When the flow valve interrupts the connection of the pump with the fuel element, there is a liquid flow in the fuel element. The flow valve creates in this case an alternative route for this liquid flow. The liquid flow in the fuel element is therein not slowed abruptly when the flow valve is converted to the first position. The prevents the liquid flow from creating forces that can dislodge the apparatus from the connecting position on the fuel element. Also when the fuel element is not activated, ingoing components can have a residual elevated temperature, which also generates a liquid flow upwards through the fuel element. To permit such a liquid flow allows for cooling the fuel element.
- According to another aspect illustrated herein, the apparatus comprises a force element that is adapted to set the flow valve in the first position and in the second position. Advantageously, this force element comprises a first component, which operates with continuous power to set the flow valve in the first position and a second component, which in an activated state operates in an opposite direction with more power than the first component in order to set the flow valve in the second position. The first component can be a spring element and the second component can be a pneumatic cylinder. Of course, the present invention is not so limited, as other types of components can be used to set the flow valve between the first position and the second position.
- According to another aspect illustrated herein, the apparatus comprises a joining portion that allows for a removable connection of the connecting elements with different shapes. For the apparatus to, in an effective way, be able to suck liquid from a fuel element, a tight connection is established between the connecting element and the fuel element. If the apparatus is to be used to clean different types of fuel elements, the apparatus can be provided with different types of connecting elements that have a shape adapted to a specific type of fuel elements. The connecting element can comprise a cup-shaped portion that is adapted to be set on or slipped over an end portion of the fuel element. Such a cup-shaped portion enables establishing a tight connection between the apparatus and the fuel element. The apparatus can comprise a gripping portion that is adapted to be gripped by a hoisting device in order to lift the apparatus to a connecting position on a fuel element and in order to lift the apparatus from the connecting position on the fuel element after a cleaning process. An existing charging machine in a reactor facility can be used in order to apply and move the apparatus between cleaning processes of individual fuel elements in a reactor tank.
- Another aspect of the present invention resides in a method for cleaning a nuclear fuel element in a liquid filled space, wherein the fuel element comprises an inner space with an opening. The method comprises the steps of connecting an apparatus to a portion of the fuel element, which comprises an opening, and creating, at least during a part of a cleaning process of the fuel element, a liquid flow through an inner space with help of the apparatus, to create, at least during a part of a cleaning process of the fuel element, a liquid flow from the inner space of the fuel element to a flow channel of the apparatus, which has an opening in connection with the connecting element. The method further comprises the step of capturing particles and deposits transported by the liquid flow from the inner space of the fuel element into a filter element in the flow channel of the apparatus. With such a liquid flow, particles and deposits can be detached from the inner space of the fuel element and be captured in the filter element.
- Advantageously, an intermittent liquid flow through the inner space of the fuel element is created with the help of the attached apparatus. Thereby, a cleaning process of the inner space of the fuel element is provided. The method can also comprise the step of connecting the apparatus to a fuel element, which is arranged in a reactor tank. Therein, the fuel elements do not need to be lifted out of the reactor tank when they are to be cleaned. However, it is possible to connect the apparatus to fuel elements, which have been lifted out of the reactor tank and placed for example in a reactor pool.
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FIG. 1 is a cutaway view of an apparatus according to the present invention in a reactor tank; -
FIG. 2 is a side view of the apparatus in a position when the apparatus is connected to a fuel element; -
FIG. 3 is a cross-sectional view through a filter element and a flow valve of the apparatus when the apparatus is in a first position; and -
FIG. 4 is a cross-sectional view through the apparatus when the flow valve has shifted to a second position. -
FIG. 1 shows areactor tank 1 for a boiling water reactor BWR. Thereactor tank 1 is shown in an open position and is arranged at a bottom surface of areactor pool 2. Thereactor tank 1 and thereactor pool 2 are filled with water. Aservice bridge 3 spans over thereactor pool 2. Theservice bridge 3 is provided with amovable charging machine 4 having atelescopic boom 5 with which it is possible to lift components up and down in thereactor tank 1. As shown, thereactor tank 1 has been partially emptied of internal components. The internal components, which are lifted out of thereactor tank 1, can be placed in different positions in thereactor pool 2. The fuel core, which is arranged in amoderator tank 6, is in this case left in thereactor tank 1. Aframe 7 forms a grid at an upper portion of themoderator tank 6 that defines the positions of a large number offuel elements 8. - During maintenance and repair work in a system that is connected to the
reactor tank 1, there is a risk that metal particles, flakes, fibers, etc. are formed, which during subsequent operations are transported by the reactor water to thereactor tank 1. Also during times when thereactor tank 1 is opened, there is a risk that particles fall into thereactor tank 1. During a subsequent operation, such particles may be circulated in thereactor tank 1 with the reactor water. In order to purify the reactor water from particles, a filter is arranged at appropriate positions in thereactor tank 1. Small particles, however, can become trapped inside thefuel elements 8. Because these particles are not circulated by the reactor water, they are not removed by conventional filters. The reactor water contains inevitable impurities that originate mainly from corrosion of material that is in contact with the circulating reactor water. During operation such impurities in the reactor water build deposits on the outer surfaces of the fuel rods. -
FIG. 1 further shows anapparatus 9, which is adapted to clean internal particles and deposits from thefuel elements 8. Theapparatus 9 is applied with help of the chargingmachine 4 at an upper end portion of thefuel elements 8 in thereactor tank 1. Thefuel elements 8 are in this case left in thereactor tank 1. It is possible, however, to lift up thefuel elements 8 and apply theapparatus 9 at thefuel elements 8 in an arbitrary position in thereactor pool 2 or in a connecting fuel pool. -
FIG. 2 shows theapparatus 9 and the top portion of afuel element 8 in more detail. Thefuel elements 8 comprise elongated tubular elements with aninner space 8 a, which containfuel rods 8 c and spacers to keep the fuel rods in a desired mutual position in theinner space 8 a. Atop plate 8 d holds a top end of thefuel rods 8 c in a desired position. During operation, thehot fuel rods 8 c heat up the reactor water that circulates through theinner space 8 a. The resulting steam and the heated water rise up in theinner space 8 a and out through anoutlet opening 8 b at an upper end of thefuel elements 8. New reactor water is fed into theinner space 8 a via an inlet opening, which is situated at a lower end of thefuel elements 8. - The
apparatus 9 has a relatively elongated construction and comprises at a first end a grippingportion 10 that is adapted to be gripped by the chargingmachine 4 when theapparatus 9 is applied to thefuel element 8. Theapparatus 9 comprises at a second opposite end, a connecting element in the form of anintake cover 11. Theintake cover 11 has a cup-shaped portion with an internal shape and size that corresponds substantially to the outer shape and size of the upper end portion of thefuel element 8. The intake cover 11 can thereby (with help of the charging machine 4) be lowered down and placed on or otherwise be affixed to the top end portion of thefuel element 8. The intake cover 11 can be provided with suitable shaped control surfaces to facilitate positioning of theintake cover 11 on thefuel element 8. Theapparatus 9 comprises anelongated flow channel 12, which extends from aninlet opening 13 in theintake cover 11 to anoutlet opening 14 in anoutlet portion 15. The grippingportion 10 is in this case attached to theoutlet portion 15. Theoutlet portion 15 has a curved shape so that theoutlet opening 14 is located alongside the grippingportion 10. The device comprises a schematically shownpump 16, which is adapted to transport the reactor water in theflow channel 12. Between thepump 16 and theintake cover 11, theapparatus 9 comprises atubular portion 17 that encloses a filter and atubular portion 18 that encloses a flow valve. The flow valve is controlled by aforce element 19. -
FIGS. 3 and 4 show cross-sectional views of the above mentionedtubular portions apparatus 9. Thetubular portion 17 comprises oneinternal wall element 20 forming a space for receiving afilter element 21, which may include a filter basket. Thetubular portion 17 is attached by means of removable attachment elements, such as screws 22. Thus, thetubular portion 17 can be removed from the apparatus when thefilter element 21 needs to be cleaned or replaced. - The
tubular portion 18 comprises a flow valve in the form of a shiftably arrangedvalve body 23. Thevalve body 23 comprises a cylindrical formed wall element and aninternal wall portion 24 that divides an internal space of thevalve body 23 into afirst chamber 25 and asecond chamber 26. Thefirst chamber 25 is provided with aperipheral opening 25 a. Thesecond chamber 26 is provided with a first peripheral opening 26 a and several other smallerperipheral openings 26 b arranged at a different level than the first peripheral opening 26 a. A radially protrudingcontrol element 27 is firmly attached to thevalve body 23. - The
force elements 19 constitute apneumatic cylinder 19 a and aspring element 19 b. Thepneumatic cylinder 19 a is firmly attached to theapparatus 9 by means of a mountingelement 28 and has a movable portion that is attached to thecontrol element 27. Thespring element 19 b is, at one end, firmly attached to theapparatus 9 by means of a mountingelement 29 and connected to thecontrol element 27 at an opposite end. Thespring element 19 b operates to shift thecontrol element 27 and thevalve body 23 downward to a first position as is shown inFIG. 3 . When thepneumatic cylinder 19 is activated thecontrol element 27 shifts upwards against the effect of thespring element 19 b, to a second position as is shown inFIG. 4 . - The
tubular portion 18, which encloses thevalve body 23 has afirst opening 30, asecond opening 31 and athird opening 32. Aflow element 33 is arranged around thetubular portion 18 at the height of thefirst opening 30 and thethird opening 32. Thetubular portion 18 comprises at a lower end a joiningportion 34 for application of anintake cover 11. The joiningportion 34 can comprisethreads 35 or other mounting elements that allow a removable application of anintake cover 11. Thereby, different intake covers 11 with suitable shapes can be attached to theapparatus 9 when the apparatus is to be connected to different types offuel elements 8. - When the
fuel elements 8 in areactor tank 1 are to be cleaned, theapparatus 9 is attached with help of the grip handle 10 of a gripper of the charging machinestelescopic boom 5. The chargingmachine 4 moves theapparatus 9 to a position substantially vertically above thefuel elements 8 to be cleaned with help of coordinate information or with information from cameras or similar detection elements, which are arranged at appropriate positions on theapparatus 9. Theapparatus 9 is then immersed into thefuel element 8 so that theintake cover 11 encloses the upper end portion of thefuel element 8 and anopening 8 b for the inner space of thefuel element 8 a. When theapparatus 9 is connected in a desired way to thefuel element 8, thepump 16 is activated. This can be done by an operator by means of a suitable control device. The operator can stand on themaneuver bridge 3 or in position at the side of thereactor pool 2. The control device can be equipped with cables that transmit control signals and power to thepump 16. - When the
pump 16 is activated, thevalve body 23 is preferably in the first position as is shown inFIG. 3 . In this position, the opening of thevalve body 25 a to thefirst chamber 25 is located in a corresponding position as the first opening of thetubular portion 30. Thereby, thepump 16 sucks in, in this case, the surrounding reactor water via theopenings first chamber 25. From thefirst chamber 25, the reactor water is sucked further into the flow channel of theapparatus 12 up to thetubular portion 17 and down into the compartment with thefilter element 21. The reactor water is then sucked through thefilter element 21 and further upwards in theflow channel 12 in the direction of thepump 16 according to the arrows inFIG. 3 . From thepump 16 the reactor water is pressed upwards in theflow channel 12 and out through the outlet opening 14 in theoutlet portion 15. The second chamber of thevalve body 26 is in constant contact with theintake cover 11 and the inner space of thefuel element 8 a. Also, when the reactor is turned off, the fuel rods can have a residual elevated temperature, which creates an upward flow of the reactor water through inner space of thefuel element 8 a. Such a liquid flow is routed from the inner space of thefuel element 8 a to the second chamber of thevalve body 26. In this case, the other smaller openings of thesecond chamber 26 b of thevalve body 26 are arranged in a position that corresponds to the position of the third opening of thetubular portion 32. Thereby, such a possible ascending flow of the reactor water can be routed from thesecond chamber 26 to the surrounding reactor water via theopening 32. When thevalve body 23 is in the first position, thepump 16 in theapparatus 9 creates no flow of the reactor water through the inner space of thefuel element 8 a. - After the
valve body 23 has been on in a specified period, which may be within the range of 1-3 seconds, thepneumatic cylinder 19 a is activated. Thepneumatic cylinder 19 a provides a force on thecontrol element 27 so that thevalve body 23 is set to the second position as is shown inFIG. 4 . When thevalve body 23 is in the second position, the second chamber of thevalve body 26 connects, via opening 26 a, to the second opening of thetubular portion 31. The second opening of thetubular portion 31 is connected to achannel portion 36, which is connected to thepump 16. At the same time, the connection between thesecond chamber 26 and the surrounding reactor water is interrupted because the opening of thesecond chamber 26 b is shifted from the third opening of thetubular portion 32. At the same time, the connection between thefirst chamber 25 with the surrounding water reactor is interrupted because the first opening of thechamber 25 a is shifted from the first opening of thetubular portion 30. Accordingly, thepump 16 can no longer suck in the reactor water through the first opening of thetubular portion 30. - In the second position of the valve body, the
pump 16 sucks in the reactor water from the inner space of thefuel element 8 a. The reactor water is sucked into theapparatus 9 with help of theintake cover 11, which is connected to the upper end portion of thefuel elements 8. The reactor water is routed from theintake cover 11 into the flow channel of theapparatus 12 viainlet opening 13. Thereafter, the reactor water reaches thesecond chamber 26. The reactor water is sucked into thechannel portion 36 from thetubular portions 18 and from thesecond chamber 26. The reactor water enters thesecond chamber 26 through theopenings filter element 21. Any particles or deposits from thefuel element 8 are trapped in thefilter element 21. The reactor water is pumped further up and out through outlet opening 14 in theoutlet portion 15. After a specified period, which may be within the range of 10-15 seconds, thepneumatic cylinders 19 a are de-activated, and thevalve body 23 is shifted back to the first position by thespring element 19 b. During a cleaning process of afuel element 8, thevalve body 23 is shifted a predetermined number of times, which may be within the range of 5-15 times, between the first position and the second position. - A cleaning process of a fuel element of the
present apparatus 9 comprises thus sucking the reactor water through the inner space of thefuel element 8 a with apump 16. Thereby, a liquid flow through thefuel element 8 is created that can detach any particles fastened inside the fuel element and deposits formed on the fuel rod surfaces. To further enhance this effect, thevalve body 23 of theapparatus 9 is shifted several times between the above mentioned positions. Thereby, an intermittent flow through the inner space of thefuel element 8 a is provided. The intermittent flow of the reactor water through the inner space of thefuel element 8 a enhances the apparatus's ability to detach particles fastened inside thefuel element 8 and to detach deposits from the fuel rods surfaces 8 c. Such detached particles and deposits are transported by the reactor water into theapparatus 9, where they are captured in thefilter element 21. When a cleaning process of a fuel element is finished, the chargingmachine 4 is activated, which moves theapparatus 9 to a not yet cleanedfuel element 8 of the reactor core. - While the invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the foregoing description.
Claims (16)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE0950720A SE534409C2 (en) | 2009-10-01 | 2009-10-01 | Apparatus and method for cleaning a nuclear fuel element |
SE0950720-3 | 2009-10-01 | ||
PCT/SE2010/051047 WO2011040873A1 (en) | 2009-10-01 | 2010-09-29 | An apparatus and a method for cleaning of a nuclear fuel element |
Publications (2)
Publication Number | Publication Date |
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US20120199161A1 true US20120199161A1 (en) | 2012-08-09 |
US9105362B2 US9105362B2 (en) | 2015-08-11 |
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US13/499,093 Active 2032-02-16 US9105362B2 (en) | 2009-10-01 | 2010-09-29 | Apparatus and a method for cleaning of a nuclear fuel element |
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Country | Link |
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US (1) | US9105362B2 (en) |
EP (1) | EP2483892B1 (en) |
JP (1) | JP5662454B2 (en) |
SE (1) | SE534409C2 (en) |
WO (1) | WO2011040873A1 (en) |
Cited By (2)
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US20180358139A1 (en) * | 2017-06-08 | 2018-12-13 | Sichuan Xingzhi Zhihui Intellectual Property Operation Co., Ltd. | System with function of bending and elongation for discharging foreign matters from nuclear reactor vessel |
US20180358140A1 (en) * | 2017-06-08 | 2018-12-13 | Sichuan Xingzhi Zhihui Intellectual Property Operation Co., Ltd. | Device for removing foreign matters in nuclear reactor vessel |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
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FR3015758A1 (en) | 2013-12-23 | 2015-06-26 | Commissariat Energie Atomique | METHOD AND DEVICE FOR CLEANING AN ASSEMBLY OF NUCLEAR FUEL PENCILS |
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2010
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- 2010-09-29 US US13/499,093 patent/US9105362B2/en active Active
- 2010-09-29 WO PCT/SE2010/051047 patent/WO2011040873A1/en active Application Filing
- 2010-09-29 EP EP10820912.3A patent/EP2483892B1/en not_active Not-in-force
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US20180358140A1 (en) * | 2017-06-08 | 2018-12-13 | Sichuan Xingzhi Zhihui Intellectual Property Operation Co., Ltd. | Device for removing foreign matters in nuclear reactor vessel |
US10784005B2 (en) * | 2017-06-08 | 2020-09-22 | Sichuan Xingzhi Zhihui Intellectual Property Operation Co., Ltd. | Device for removing foreign objects from nuclear reactor vessel |
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Also Published As
Publication number | Publication date |
---|---|
JP5662454B2 (en) | 2015-01-28 |
EP2483892B1 (en) | 2016-08-10 |
WO2011040873A1 (en) | 2011-04-07 |
SE534409C2 (en) | 2011-08-09 |
JP2013506832A (en) | 2013-02-28 |
EP2483892A4 (en) | 2014-12-10 |
EP2483892A1 (en) | 2012-08-08 |
SE0950720A1 (en) | 2011-04-02 |
US9105362B2 (en) | 2015-08-11 |
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